Citrus Greening (Huanglongbing): A Serious Threat to the Florida Citrus Industry1
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Huanglongbing History
In 1995, the official name for greening became Huanglongbing (HLB)
The vector, Asian citrus psyllid, was first found in Florida in 1998
HLB was first detected in residential areas in South Florida in August 2005
As of October 2006, HLB affected trees had been found in twelve counties
By October 2007, affected trees had been discovered in twenty-eight counties
Thirty-two counties had confirmed greening in their area by the end of 2008
By February 2010, thirty-four counties had at least one positive confirmed HLB affected tree
HLB is now confirmed in all commercial citrus growing counties in Florida
Currently, identified in most non-commercial citrus growing counties in residential properties
Huanglongbing Biology
A disease caused by a phloem-limited bacterium affecting all citrus cultivars
The rod-shaped, Gram-negative bacterium is named Candidatus Liberibacter asiaticus
Bacterium does not move between trees without the insect vector or through grafting
The bacteria are present in symptomatic tissues in low numbers
Phloem tissue is damaged when bacteria are present
Starch accumulates to toxic levels in plant cellsExcessive phloem tissue is produced in infected trees
Bacteria are at their highest levels in young asymptomatic tissues and appear to die as tissues age and become symptomatic
Changes to the plant tissue begin in the early infection before symptoms
Varieties Affected
All citrus varieties and rootstocks can be affected by HLB
Affects plants in the Rutaceae family (ex. box orange and orange jasmine)
Greening Vector
Asian citrus psyllid (Diaphorina citri)
Five nymphal stages
Numerous generations per year
Egg to adult in 2 weeks at 75°F to 85°F
Egg stage lasts an average of 3 to 4 days
Duration of the nymphal stages is about 12 to 14 days at 82°F
Adult psyllids may live for several months in cool temperatures
Psyllids can acquire the bacterium from infected trees, regardless of whether symptoms are present on the tree
The longer psyllids remain uncontrolled and are allowed to feed on infected trees, the higher the chance that those psyllids will acquire and spread HLB to other trees
Psyllid populations are best managed by controlling adults prior to the presence of new flush which facilitates rapid population growth
Chemical control of the psyllid and removal of infected trees are the only methods currently available to manage the spread of greening
Commercial Management
For detailed information, please see UF/IFAS Guidance for Huanglongbing (Greening) Management (https://edis.ifas.ufl.edu/hs1165)
Citrus Health Management Areas (https://crec.ifas.ufl.edu/extension/chmas/)
Residential Management
Remove infected trees
Use of disease-free nursery trees (a certified nursery tag should be attached to tree at time of purchase)
Use horticultural oil sprays to manage psyllid populations
When applying pesticides, remember the label is the law
The Florida Department of Agriculture has a release program for the Tamarixia radiata, a beneficial insect of the psyllid. For more information, visit https://www.freshfromflorida.com/
Greening Symptoms
Symptoms can be found year round, but are more prominent September through March
Diagnostics
Southern Gardens Diagnostic Laboratory
111 Ponce de Leon Ave.
Clewiston, FL 33440
(863) 902-2249
Contact: Mike Irey
msirey@ussugar.com
Florida Division of Plant Industry
PO Box 147100
Gainesville, FL 32614-7100
(800) 282-5153
UF Plant Diagnostic Center
Building 1291, 2570 Hull Rd.
Gainesville, FL 32611
352-392-1795
Before sending samples, contact the testing facility to obtain proper sampling procedures, submission guidelines, and fees.
Contacts
UF/IFAS Citrus Research and Education Center
Jamie Burrow
Extension Program Manager
863-956-8648
Megan Dewdney, Ph.D.
Plant Pathologist
863-956-8651
Tripti Vashisth
Horticulturist
863-956-8846
Lauren Diepenbrock, Ph.D.
Entomologist
863-956-8801
UF/IFAS Indian River Research and Education Center
Rhuanito "Johnny" Ferrarezi, Ph.D., Horticulturist
772-577-7376
Liliana Cano, Ph.D., Plant Pathologist
772-577-7350
Jawwad Qureshi, Ph.D., Entomologist
772-577-7339
UF/IFAS Southwest Florida Research and Education Center
Ute Albrecht, Ph.D., Plant Physiologist
239-658-3422
Fernando Alferez, Ph.D., Horticulturist
239-658-3426
Ozgur Batuman, Ph.D., Plant Pathologist
239-658-3408
Phil Stansly, Ph.D., Entomologist
239-658-3427
UF/IFAS Extension Offices with Citrus Agents
Hardee, Hendry, Highlands, Lake, Polk, St. Lucie, Sumter
Websites
UF/IFAS Extension Citrus Agents
http://citrusagents.ifas.ufl.edu
UF/IFAS Citrus REC
http://www.crec.ifas.ufl.edu
UF/IFAS Southwest Florida REC
https://swfrec.ifas.ufl.edu/
Local UF/IFAS Extension Office
http://sfyl.ifas.ufl.edu/find-your-local-office/
For more information, please contact the UF/IFAS Citrus Research and Education Center, Lake Alfred 863-956-1151